In these years, the number of people with mental disorders is increasing, and it becomes important to appropriately grasp the mental and physical health states of individuals. To acquire and manage the mental and physical states, for example, Patent Literature 1 describes a technique which acquires the health states (sensible data) that an individual subjectively feels and the time or speed (performance data) that the individual do a certain cognitive task, and accumulates and displays those data. According to this method, it is expected that such sensible and performance data lead to an early detection of an abnormality such as the individual's indisposition or mental failure. However, the method does not directly measure mental and physical complaints, and it is difficult to eliminate the possibility that items of sensible data derived from subjective answers are greatly varied depending on individuals.
On the other hand, Patent Literature 2, for example, describes a biophotonic measurement device which visualizes two-dimensional images of information inside a living body by measuring the living body using light at a plurality of wavelengths in visible to infrared region. In the biophotonic measurement device described in this Patent Literature, lights are generated by semiconductor lasers, the generated lights are guided through optical fiber bundles, a plurality of places of a subject are irradiated with the lights, lights transmitted through or reflected off the inside of the living body are received at a plurality of places of the living body, the received lights are guided to and detected at photodiodes through another optical fiber bundles, the lights is converted into living body information such as blood circulation, hemodynamic responses, and changes in haemoglobin concentration from the detected lights, and this living body information is formed in a two-dimensional image. Since such a biophotonic measurement device has the characteristics that the device is noninvasive and low constraint to living bodies, the device is suited to the assessment of an individual's mental state and living body information under a usual environment as compared with a large scale measurement technique such as functional magnetic resonance imaging (fMRI).
Patent Literature 3, for example, describes a method for assessing a mental state and living body information under a usual environment using this biophotonic measurement device. The method described in Patent Literature 3 is in that a verbal working memory task (a task that requires a phonological loop), which uses a human working memory function, and a nonverbal working memory task (a task that requires no phonological loop) are given and frontal lobe activities in association with the memorization, retention, and recollection of the working memory tasks are measured by a biophotonic measurement technique. For the characteristics of the frontal lobe activities shown in Patent Literature 3, the frontal lobe activities in association with the memorization and retention of the verbal working memory task have a negative correlation with a score of “depression-dejection” (POMS_D) obtained by a standardized short form of the Profile of Mood State (POMS) questionnaire, whereas the frontal lobe activities have a low correlation with recollection. On the other hand, the frontal lobe activities in association with the nonverbal working memory task have no significant correlation with POMS_D. Both working memory tasks have different objects but the memorization and retention features are identical, therefore, relative frontal lobe activities from the verbal and nonverbal working memory tasks are proposed to express quantitative values that have the relationship to mood among subjects. This method has advantages in that it does not need to induce any change in mood prior to measurement and uses a low constraint and noninvasive biophotonic measurement technique. In other words, with the use of the method, it is expected to implement a mood self-check system applicable to mental healthcare by directly acquiring quantitative values reflecting a usual mod state without any stimuli inducing changes in mood.